The approach we present was first proposed by Ref. [1]}, [2]}, [3]}. It was recently applied to find the entanglement entropy of JT gravity [4]} and generic fixed area states [5]}. Similar techniques were used to calculate the negativity [6]}, [7]}. This powerful approach enables us to write down the Schwinger-Dyson equation for the resolvent of \(\rho _{AB}\) , which then gives full information about the entanglement spectrum.
